The traditional method of extracting bitumen from mined oil sands involves hot water, solvents and usually chemical additives. The resultant slurry is agitated, and the bitumen froth is skimmed from the top.
Using water in the extraction process creates significant environmental problems. Waterless systems have been proposed, such as are described in U.S. Pat. No. 3,114,694 (Bergougnou et al.) entitled “Process for the recovery of bitumen from tar sands utilizing a cooling technique” and U.S. Pat. No. 4,498,971 (Angelov et al.) entitled “Separation of bituminous material from oil sands and heavy crude oil.”
Furthermore, when oil sands are mined, it is common to have large pockets or lenses of clay in the mined material, which are introduced into the stream of material being processed. The efficiency of the process is affected by the ratio of bitumen to other materials, such as sand and clay.